This invention relates to leave-on, topical antimicrobial compositions that do not require water for antimicrobial effectiveness when applied to the skin. Specifically, the antimicrobial compositions of the present invention use an alcohol based solution to provide an essentially immediate reduction of microorganisms on the skin, a silicone additive to aid in the drying process, and an emollient to leave the skin feeling moisturized.
It is well known that cleansing one""s hands with soap and hot water is an effective means of reducing microorganisms on the skin surface. However, if the hands are not thoroughly dried, the trace water residue can harbor bacteria. While this may not pose a serious threat to the population at large, in a hospital setting where the population is more prone to infection, it is desirable to minimize any contamination risks.
In the past few years, research efforts have been directed toward formulating a liquid cleansing product that will effectively sanitize the skin without the use of water. Many of these liquid cleansing products incorporate relatively high concentrations or weight percentages of alcohols in the compositions. The alcohols allow the product to dry quickly, but also cause the skin to dehydrate to an unacceptable degree, irritating the skin and causing it to crack and chafe.
The present development relates to a liquid cleansing product that is not water-based. When used topically, the cleansing product effectively reduces the level of microbes on the skin in a relatively short wash time. Further, the cleansing product dries quickly without causing damage and drying to the skin with repeated use. As an added benefit, the cleansing product may provide a moisturizing benefit to the skin.
The present invention provides an antimicrobial sanitizing cleanser composition comprising an effective amount of alcohol to produce a reduction in microorganisms on the surface of the skin and an additive to maintain the skin pH in the range of from about 4.0 to about 6.0. Specifically, an effective amount of lactic acid, fumed silica, sodium lactate or a combination thereof can be added to balance the skin pH. The cleanser composition may further include silicone to aid further the drying process, and emollients or oils for skin moisturizing. The present invention also relates to methods for reducing the level of microorganisms on the skin using the leave-on antimicrobial compositions described herein.
The present development is a composition for a sanitizing hand cleansing product that is not water based. The product is alcohol based with additives to allow the skin to maintain a pH at from about 4.0 to about 6.0, thus reducing the bacteria count on the skin while maintaining the normal flora of the skin. The composition also includes a silicone component that aids in the drying process, and may also contain emollients which leave the skin feeling moisturized and refreshed. The antimicrobial compositions of the present invention are highly efficacious for reducing the number of microorganisms on the skin while also being moisturizing and protecting to the skin. Further, since the compositions are not water based, several additional advantages are gained over hand cleansing products containing added water. With none to negligible amounts of water present in the compositions of the present invention, the rate of evaporation of the composition from the skin is more consistent than with water present. The humidity of the surrounding air affects the evaporation rate of the water. Thus, a composition containing a significant amount of water would evaporate more slowly from the skin in conditions of higher humidity. Not only does this require the consumer to spend more time rubbing the compound on the skin, it also leaves a tacky or clammy feeling on the skin. The compositions of the present application do not suffer from these detriments since there is no added water in the compositions and the evaporation rates of the alcohol and volatile silicone components are not affected by air humidity.
The sanitizing hand cleanser includes one or more alcohols to provide antimicrobial functionality, to assist in the drying process, and to serve as a solvent. Preferably, the alcohols are approved for use on human skin, such as ethanol, isopropanol, or a combination thereof. The alcohols are present in the formulation at a concentration of from about 60 wt. % to about 90 wt. %.
The hand cleanser also includes one or more additives to allow the skin to maintain a pH of from about 4.0 to about 6.0, such as fumed silica, lactic acid, sodium lactate or a combination thereof. In this pH range, the bacteria count on the skin is reduced while the normal flora of the skin is maintained, potentially providing additional antimicrobial benefits for the cleansing product. An effective amount of additive is included in the formulation to maintain the desired skin pH range, and the amount of additive may range from about 0 wt. % to about 12 wt. %, depending on the additive or combination of additives included in the formulation.
One or more silicone-based materials are included in the hand cleanser formulation to further aid the drying process. The volatile silicones utilized in the compositions of the present invention have a lower heat of evaporation than alcohol, and as such do not create the unpleasant cooling effect on the skin observed with pure alcohol formulations. Further, use of silicone-based materials can lower the surface tension of the fluid composition. This provides greater contact with the skin and therefore more of the fluid can come in contact with detrimental microorganism to provide better overall killing activity. The silicone-based materials, such as cyclomethicone, trimethylsiloxy silicate or a combination thereof, are included in the formulation at a concentration of from about 4 wt. % to about 50 wt. % and more preferably from about 5 wt. % to about 35 wt. %, and even more preferably from about 11 wt. % to about 25 wt. %.
As is known in the art, humectants are added to assist in the retention of liquids within the product, and thickening agents are added to modify the product viscosity. In the present development, any humectant or thickener which does not significantly alter the ability of the formulation to maintain the skin at the desired pH can be used, with the humectant included at a concentration of from about 0 wt. % to about 5 wt. % and the thickener included at a concentration of from about 0 wt. % to about 6.5 wt. %. The thickener may be a cellulose-based material, fumed silica, or a combination thereof, such as methyl cellulose added at concentrations of about 0 wt. % to about 1.5 wt. % used in combination with fumed silica added at concentrations of about 0 wt. % to about 5.0 wt. %.
The hand cleanser may also optionally contain additional antimicrobial agents to enhance the germicidal effects of the alcohol. Exemplary agents include para-chloro-meta-xylenol (PCMX), chlorhexidene gluconate (CHG), triclosan, quaternary ammonium salts like benzalkonium chloride, benzethonium chloride and cetrimide, and other agents as are generally known in the art. These agents may be employed in the composition at a range of between about 0.25 wt. % and about 10 wt. % or at a concentration known to be effective as an antimicrobial. As a representative and non-limiting example, PCMX can be included in the composition of the present invention at a concentration known to provide safe antimicrobial action of from about 2 wt. % to about 3.75 wt. %.
Optionally, emollients and aesthetic additives, such as fragrance and/or colorants may also be added to the sanitizing hand cleanser formulation. Emollients or moisturizing agents, fragrance and colorants are added as necessary and at concentrations for consumer acceptance. For example, the formulation may include from about 0 wt. % to about 1.5 wt. % fragrance, dye or a combination thereof. The formulation may also include from about 0 wt. % to about 5 wt. % of additional emollients, such as, tea tree oil, hemp oil, aloe-based oil, lanolin, jojoba, chamomile, floral oils, herbal materials or a combination thereof are added to the cleansing product to further aid skin moisturization.
The product is prepared by combining the alcohols, the silicone-based materials, the humectants, and the lactic acid or sodium lactate at ambient temperature in a batch mixing vessel and mixing until well blended. Then a portion of the alcohol mixture is removed to a separate mixing vessel and the thickening agents are added, with mixing, until the mixture thickens slightly. Optionally, the fumed silica is then added to the thickening agent mixture to cause the mixture to thicken further. The thickening agent mixture is then combined with the remaining alcohol mixture while maintaining continuous mixing. The resulting product should have a viscosity that allows the product to be dispensed through a hand-pump, such as is commonly used on liquid soap dispensing bottles. For example, the viscosity could range from about 100 centipoise (cp) to about 100,000 cp at about 25xc2x0 C. The fragrance may be added at any time that allows for good mixing, such as with the alcohol.
The finished product may be incorporated into applicators for specific uses. For example, the product may be added to the sponge of a surgical scrub brush. The brush with incorporated hand scrub can then be used by surgical personnel as part of their aseptic prepping prior to surgery. Alternatively, the product can be incorporated into a woven or non-woven wipe. The wipes can be packaged either individually or together. The wipes with sanitizing cleanser make for a convenient product for cleansing a practitioner""s hands or a local portion of a patient before or after examination.